Yowza! 12 foods that pack on pounds

Why are Americans so fat? Too much food and not enough exercise are the usual answers. But in a finding that has surprised some experts, Harvard scientists are reporting that 12 foods in particular seem to cause people to pack on the pounds.

Keep clicking to find out what you may want to avoid if you want to keep off excess weight...

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12. Butter

Dairy foods like butter and cheese were linked with long-term weight gain - no surprise there. In the Harvard study, people who ate a lot of butter gained about 0.30 pound every four years. But there was one notable dairy exception: yogurt. People who ate a lot of it were less likely to put on weight, the study showed.

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11. Fruit juice

10. Fried foods

Fried food is as American as apple pie. But the study revealed that eating fried foods at home added 0.36 pound every four years. Eating lots of fried food out at restaurants added 0.28 pound every four years.

Time to ditch the mini fryer?

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9. Refined grains

One reason refined grains are linked to weight gain is that Americans eat so much of them, displacing foods that are healthier, including fruits and vegetables. The refining process often strips away the benefits of grain, leaving what some experts call "bad carbohydrates." Daily servings of refined grains added 0.39 pound every four years.

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8. Sweets and desserts

Cakes, pies, cookies, candy - even children know too much of these can make you chubby. But it's hard for folks to abandon that sweet tooth. Eating sweets daily added 0.41 pound every four years, according to the study.

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7. Potatoes

The study showed that all types of potato dishes had an impact on weight gain. Boiled, baked, mashed? Didn't seem to matter. Getting a daily fix of potatoes added 0.57 pound of weight every four years.

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6. Trans fats

Some states and cities have banned trans fat - which is often found in deep fryer shortening and processed foods. But plenty of people are still eating them. Eating trans fats added on 0.65 pound of weight every four years, the study showed.

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5. Processed meat

Cold cuts and hot dogs may be staples of sandwiches and school lunches. But they are high in calories and saturated fat, not to mention sodium. The study showed that eating lots of processed meats tacked on 0.93 pound every four years.

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4. Unprocessed red meat

Where's the beef? If it's on your plate too often, you may be risking weight gain. In the study, eating lots of red meat contributed to a weight gain of 0.95 pound every four years.

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3. Sugar-sweetened soda

Fruit juice can pack on the pounds, but not as much as soda. Daily consumption of sugary drinks added exactly one pound every four years, according to the study.

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2. Potato chips

Chips may be thin, but not people who eat lots of them. In the study, daily chip eating brought a 1.69 pound weight gain every four years.

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1. French fries

Are you a fan of french fries? Watch out. In the study, people who ate lots of fries gained more than three pounds of body weight every four years. Over the study's 20-year-period, that meant people who ate more fries put on more than 16 extra pounds from this food alone. No other food came close.